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PSoC 4 MCU

MrMa_286121
New Contributor II

 Hello!

   

I need to install three input switches corresponding to which there are three LEDs that show the status of the switches.

   

I was certain to use macanical switches. But just got to know a bit more about the CAP SENSE capability of PSoc chips.

   

So m thinking to give a try to the CAPSENSE version.

   

 

   

Simplified scenario...

   

There's a PCB containing three LEDs

   

Above the LED is 1mm thick diffusing epoxy

   

Above the epoxy is 1mm transparent glass. The user will touch this glass.

   

I want to make the capsense pads just below the LED. Size of pad is approx 4mmx2mm

   

A 3D photo is attached for better understanding.

   

 

   

Am I thinking in the correct direction or am I incorrect in the approch?

   

I have zero experience with cap sense.

   

Please help/guide...

   

Thanks!

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8 Replies
JoMe_264151
Expert II

This appnote can be of interest for you.

   

 

   

Bob

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ETRO_SSN583
Esteemed Contributor

The tuning guide also useful -

   

 

   

    

   

          http://www.cypress.com/?rID=105244

   

 

   

Regards, Dana.

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MrMa_286121
New Contributor II

 Very helpful indeed! Thanks...

   

Another thing...

   

If we use capsense, then can we use the IDAC for analogue purpose, or will it be 'taken over' by the capsense block?

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JoMe_264151
Expert II

There are four IDACs within a PSoC4: two 8-Bit and two 7-bit ones. You may use two of those for your own program (one 7-bitand one 8-bit) and the other you may use for capsense. When in need of another 7-bit IDAC then you may use that  with a little bit restricted configurations of the CapSense. See CapSense datasheet, chapter "CapSense Analog System" on pg. 74.

   

 

   

Bob

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MrMa_286121
New Contributor II

Yes, got it...

   

Thank you!

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ETRO_SSN583
Esteemed Contributor

 4 IDACs or 2 IDACs ? From the TRM -

   

 

   

23.6 General-Purpose Resources
- IDACS

   


If the CapSense block is not used for touch sensing, the two
IDACs can be used as general-purpose analog blocks.
The 8-bit IDAC can operate in either 0 to 306 µA (1.2 µA/bit)
or 0 to 612 µA (2.4 µA/bit) ranges. The 7-bit IDAC supports
0 to 152.4 µA (1.2 µA/bit) and 0 to 304.8 µA (2.4 µA/bit)
ranges.

   


Both the 8-bit and 7-bit IDACs can connect to GPIOs using
AMUXBUS A and AMUXBUS B. It is also possible to con
nect both IDACs to a single AMUXBUS. The IDACS can
operate in three different modes: CSD-only mode, General
purpose (GP) mode, and CSD and GP mode. Table 23-1
describes how IDAC1 and IDAC2 are connected to AMUX
BUS A and AMUXBUS B in each of these modes.

   

 

   

 

   

   

From 42xx resources page -

   

   

 

   

8-bit CapSense IDACs          :    1 :    0 :    1 : 100.00%

   

7-bit CapSense IDACs          :    1 :    0 :    1 : 100.00%

   

 

   

Regards, Dana.

   
         
   


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JoMe_264151
Expert II

I was using a PSoC4-M which has got some more IDACs.

   

 

   

Bob

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ETRO_SSN583
Esteemed Contributor

@MrinalMani, are you using a PSOC 4 M series or just plain PSOC

   

4100/4200 part ?

   

 

   

Regards, Dana.

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